A variety of sensors is commonly used in sensor hubs for user devices, such as smartphones, tablet computers, “2 in 1” mobile computing devices, or wearable devices. For example, proximity sensors, gyroscopes, temperature sensors, heart rate sensors, and the like may be used in these user devices.
The role of sensors in the user devices may often involve detecting a change in a state of a particular process that may be external to the user device. For example, a proximity sensor in a mobile computing device may detect the presence of human tissue (like a hand, finger, or face, among others) when it is closer than a specific threshold distance mandated by governmental agencies, such as Federal Communications Commission (FCC) and/or European Conformity (CE) regulations. Typically, upon the sensor's detection of human tissue in unsafe proximity to the user device, the circuitry controlling the user device's transmitter that includes radio frequency (RF) power amplifier gain, may turn the power amplifier down (or off), ensuring the RF power radiated by the device does not damage the detected human tissue.
Upon failure of a proximity sensor either due to a manufacturing defect or any environmentally-induced effect in-field, the detection of human tissue may no longer be possible. Currently available solutions rely on the assumption that a sensor, such as a proximity sensor, may always work. As a result, in the event of either a proximity sensor failure or a failure in the communication channel between the proximity sensor and the processor running the operating system of a mobile device, while the RF power amplifier is configured to be operating in a high-power output mode, the presence of a human tissue within the FCC or CE mandated threshold distance may be undetected. Consequently, the RF power emitted by the mobile device may remain high even when the human tissue is closer than the mandated threshold distance, thereby violating FCC and CE regulations and increasing the risk of serious bodily injury due to long-term radio frequency power exposure of the human tissue of the user.